From testosterone replacement to drugs like Viagra, sexual enhancement is a multibillion-dollar business in the United States.

But Chris Kilham, a 62-year-old from Massachusetts who refers to himself professionally as the “medicine hunter,” is hoping to introduce a natural, safer alternative that also works for women and could blow the market wide open.

It’s called tongkat ali, the root of an exotic tree that grows in the Malaysian rainforest.

“You take people who have low libido, you give them tongkat ali,” Kilham said. “It’s Chinese New Year’s fireworks in their pants. It works.”

Kilham is one of the herbal industry’s hired guns. He scours the globe investigating natural remedies to make people younger, stronger and sexier.

His specialty is libido-enhancing botanicals and he has staked his reputation on tongkat ali. It’s a remedy already successful in Malaysia that most Americans have never heard of, but he wants to make it a household name and he has convinced one of the herbal industry’s biggest players, Naturex, that they will make millions if they back his plan.

"Nightline" followed Kilham on a rugged journey into tongkat ali’s natural habitat to search for a steady source that can sustain American demand. Wild tongkat ali is prized for its potency and so far, no one has figured out how to successfully farm it.

“Are we damaging the wild’s supply? Are we harvesting just enough that it’s sustainable? This is the one remaining unanswered question for me,” Kilham said.

Tongkat ali does not treat erectile dysfunction, so it is not a replacement for Viagra. But Ong Boon Kean, a senior researcher at the Forest Research Institute of Malaysia, has studied the effects of tongkat ali and said it can actually boost low testosterone and sperm count.

“There are lots of different ways to get a sexual function, but certainly boosting testosterone is one of them,” Kilham told “Nightline.”

And he says, unlike most prescription sexual enhancers on the market, this one helps women too.

“In this endless, failed quest that the pharmaceutical companies have had to find a female Viagra,” he said, “guess what, this is that thing.”

Up to one in three American women suffer with low sexual desire, and Alisa Roberts, a 34-year-old California mom, is one of the few Americans who actually managed to get her hands on tongkat ali.

“After having my first child, I just noticed that I didn’t want to have sex,” Roberts told “Nightline.” “Even just the thought of it made me feel exhausted.”

Roberts said she scoured the internet in search of various exotic remedies before she decided to experiment with tongkat ali.

“It was coined the herbal Viagra, so it kind of piqued my interest,” she said.

Within five days of ingesting a pill form of tongkat ali, Roberts said her husband noticed something was different about her.

“I just felt like I had more desire for him,” Roberts said.

The science is still shaky, but there are several studies, some of them industry-sponsored, that support the root’s libido-enhancing claims.

While it is not a substitute for Viagra, Kilham said tongkat ali is a safe, long-term alternative to attaining a healthier sex drive.

“People are disillusioned with pharmaceuticals. The safety part is just so startlingly evident,” Kilham said.

Over 100,000 people die every year from the proper use of prescription medications. But herbs do have their own set of risks.

Critics complain that the U.S. Food and Drug Administration oversight of the industry is far too lenient, relying on manufacturers to self-police.

“Herbal supplements are not drugs so they should not be regulated like drugs,” Naturex sales director David Yvergniaux told “Nightline.”

Yvergniaux said applying pharmaceutical standards to herbal medicine would make supplements unaffordable.

Kilham’s employer is the largest botanical extract manufacturer in North America. They sell processed herbs to most major brands.

“Those products have been used for hundreds of years,” he said. “Traditional use is the best proof for safety, but what we do on top of this is make sure it has no contaminants.”

After Kilham’s expedition, Naturex decided to roll the dice on tongkat ali, which means California mom Alisa Roberts won’t have to search far for a little boost in her sex drive.

“Our sex life is great now,” she said. “[It] fulfills his needs and is fulfilling mine because now I have a need that needs to be met too.”

Now Roberts wants to spread the love to other couples who need help regaining their mojo, so she started a blog called The Libido Café that explores natural remedies for the bedroom and beyond.

“For every ailment, there is a herb,” she said, “and people are starting to pay attention.”